Note: Descriptions are shown in the official language in which they were submitted.
CA 0221376~ 1997-08-20
Submersible motor-driven pump with float switch
The invention relates to an electric submersible motor-driven
pump which can be switched on and off by means of a liquid
level-dependent float switch, said float switch consisting of
a float which is arranged in movable fashion in the direction
of buoyancy in a housing open to the liquid and which interacts
with a liquid-tight encapsulated switch for switching the pump
motor on and off.
A submersible motor-driven pump of this kind is familiar from
DE-PS 33 32 050, for example. In this submersible motor-driven
pump, the f-loat can be accommodated in a chamber attached to,
or integrated in, the housing, while the switch for switching
the pump on and off is located in the upper section of the pump
housing. The switch operated by the float acts directly on the
power supply of the pump motor, interrupting it when the float
reaches its lower position.
Pumps of this kind are used, for example, for draining gully
holes, the pump being switched off automatically when the water
level in the gully hole drops below a certain point. These
pumps can also be used for delivering a certain quantity of
liquid, independently of the liquid level, if they are switched
on or off by additional devices, independently ~F ~ s~ n
of the float, although a pump of this kind is essentially
CA 0221376~ 1997-08-20
unsuitable for applications of this kind. It is also relatively
e~pensive as a result of the integrated switch or float.
In addition, float switches for switching submersible motor-
driven pumps on and off automatically have also become known
which consist of a switch located in a float, mounted in mov-
able fashion on the pump housing by means of a flexible cable,
which transmits a control pulse to a switchable adapter plug,
located between the pump motor and the power mains, as a func-
tion of its position in the liquid. However, in the case ofpumps of this kind, there must always be sufficient space in
the shaft or sump for the float to move freely.
As soon as the free movement of the float is obstructed by
shaft walls or floating objects, it can no longer be guaranteed
that the pump is switched off or on automatically.
Additionally, the cable containing the electrical leads is at
risk of fracturing in the long term as a result of the alter-
nating bending stress, meaning that problems can arise withthese float switches after a certain period of use.
In the case of the pumps with integrated switches, described
first and reflecting the prior art, there is furthermore a
problem if the pump breaks down and the cause of the fault is
to be determined. The problem lies in the fact that it is
impossible to establish directly whether there is a fault in
the pump control, in the form of the switch, or whether the
pump drive motor is faulty. The pump housing has to be opened
in order to establish the cause and, in the case of many modern
pump designs, this should be avoided if at all possible for
safety reasons, because tightness problems and, consequently,
insulation problems can occur after reassembling the pump
housing. For this reason, the housings used often cannot be
opened, at least not by a layman.
CA 0221376~ 1997-08-20
The invention is based on the task of creating an electric
submersible motor-driven pump which is inexpensive and offers
improved functional characteristics.
In accordance with the invention, this task is solved in that
the float and the switch are accommodated in a separate compo-
nent that can be fastened to the housing of the submersible
motor-driven pump in detachable fashion, the switch interacting
with a switchable adapter plug located outside the medium being
pumped, between a power source and the pump motor.
Thus, in the submersible motor-driven pump in accordance with
the invention, the controller which, in the form of the iiquid-
tight encapsulated switch, interacts with the float, is housed
in a separate component which can be retrofitted to the pump,
if this is practical for the des red application. The pump can
thus be manufactured inexpensively without this retrofit unit
and used for the vast majority of applications.
If, however, the pump is subsequently to be converted for auto-
matic operation, this simply requires fastening the separate
component containing the float and the switch to the pump hous-
ing in detachable fashion. In this context, the control pulse
of the switch is connected to a switchable adapter plug,
located between the power source and the pump motor. This per-
mits very simple checking of the pump function, since removing
the adapter plug and the separate component makes it very easy
to establish whether the electric motor of the submersible pump
is faulty or whether there is a fault in the control se~tion.
The movable arrangement of the float in the housing open to the
liquid, where there may be slits for the liquid in the lower
region, for example, simultaneously guarantees that the float
can move without hindrance in the direction of buoyancy, mean-
ing that there is no need to pay attention to the freedom ofIn~vem~n~ ~r ~he rl~Ja~ thi., i~, a]w~ys ens~ l wi~h th~
vice in accordance with the invention.
CA 0221376~ 1997-08-20
In order to guarantee reliable activation of the pump when the
liquid level rises, the float preferably displays different
cross-sections over its length in the direction of buoyancy. As
a result, the buoyancy force of a rising liquid level does not
act proportionally on the float; instead, the buoyancy is in-
creased more than proportionally by the areas with a wider
cross-section, meaning that sufficiently high buoyancy forces
exist with relatively short switching paths.
The float is preferably designed as a one-piece plastic body
and can consist of a lower float element, widening at right
angles to the direction of buoyancy, a long section leading
upwards from there, and an upper float element, widening at
right angles to the direction of buoyancy, at a certain dis-
tance from the lower float element. As a result, the float iscaused to rise when the liquid level reaches the upper widened
area, at the latest.
The switch located in the separate component in liquid-tight
fashion is preferably designed as a microswitch with a switch-
ing lever which is forced up by the rising float, thus causing
the power supply to be enabled via the switchable adapter plug.
In order to ensure easy and simplified mounting of the separate
component, this can expediently be slipped onto guide rails of
the pump housing, or it can be fixed in detachable fashion at
a defined position on the guide housing, for instance with the
aid of snap-on elements.
An example of the invention is illustrated in the drawings and
explained in detail below on the basis of the drawings.
The drawings show the following:
~5 Fig. 1 a lateral section through an electric submersible
motor-driven pump with attache~ .~ep~r~t~ r~mp~n~n~
housing a float and a liquid-tight switch,
- - ' CA 0221376~ 1997-08-20
Fig. 2 a section through the middle section of the separate
component, and
Fig. 3 a section through the upper section of the submers-
ible motor-driven pump and the separate component as
per Fig. 1.
Figure 1 illustrates an electric submersible motor-driven pump
1, where an electric motor 3 is located inside a housing 2 to
drive an impeller 4, with the aid of which liquids can be con-
veyed. The power to the electric motor 3 is supplied via a
cable lead 5, which can be connected to a power source (not
shown).
Mounted on the housing 2 of the submersible motor-driven pump
1 in detachable form is a separate component 6, consisting of
a-long housing section 7, open to the liquid, for accommodating
a float 8 and a liquid-tight encapsulated head section 9 for
accommodating a switching unit 10.
The switching unit 10 comprises a microswitch 11, which is
actuated by means of a switching lever 12.
The switching lever 12 is located inside a rubber cuff 13 or a
plastic hose in order to seal it.
The upper, tapered end 14 of the float 8 lies against the
switching lever 12, meaning that the switching unit 10 is
actuated by the movement of the float 8 in or against the
direction of buoyancy.
The float 8 consists of a widened lower float element 15 and a
similarly widened upper float element 16, arranged at a dis-
tance from the lower float element 15.
The separate c~rnponent 6 can be slid onto ~ lo r,~ F
the housing 1 with the aid of a claw 17 and locked in a speci-
' CA 0221376~ 1997-08-20
~ . 6
fic position.
A liquid-tight cable 19 leads out of the head section 9 of the
separate component 6 and is connected to a switchable adapter
- 5 plug (not shown) which is located between the power source and
the electric motor 3 of the submersible motor-driven pump.
When the float 8 moves downwards as a result of gravity when
the liquid level is correspondingly low, the switching unit is
actuated via the switching lever 12 in such a way that the
switchable adapter plug (not shown) interrupts the power supply
to the electric motor 3, this causing the pump to be switched
off. The switching operation for enabling the power supply
takes place accordingly when the liquid level rises.
. -. CA 02213765 1997-08-20
List of reference numbers
1 Submersible motor-driven pump
2 Housing
3 Electric motor
4 Impeller
Cable lead
6 Separate component
7 Long housing section
8 Float
9 Head section
Switching unit
11 Microswitch
12 Switching lever
13 Rubber cuff
14 Upper end
Lower float element
16 Upper float element
17 Claw
18 Guide rail
19 Cable
